Agriculture Canada study | Researchers have found possible sensitivity in Group 2 resistant kochia to other herbicides
A new discovery by Agriculture Canada researchers could help prairie producers better manage harmful kochia weed populations.
Officials have documented for the first time negative cross resistance in ALS-inhibitor (Group 2) resistant kochia. Negative cross resistance when resistance to one herbicide results in increased susceptibility to another.
The study, recently published in Weed Technology, examined plants from six kochia populations collected across the Prairies, where the vast majority of kochia populations are resistant to Group 2 herbicides.
The weed can have a dramatic impact on yields, is drought and saline tolerant and tumbles across the Prairies, spreading thousands of seeds every yea .
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Greenhouse experiments last winter in Saskatoon tested six herbicides with different modes of action against Group 2-resistant and susceptible plants.
The experiment found that Group 2-resistant plants with a common and naturally occurring mutation — dubbed Trp574 — were 80, 60 and 50 percent more sensitive to carfentrazone, a Group 14 PPO inhibitor, and pyrasulfotole and mesotrione, Group 27 HPPD inhibitors, respectively.
“We observed this phenomenon, but we’re wondering what’s the physiological or biochemical explanation as to why these Group 2 resistant plants with this particular mutation appear to be more sensitive to herbicides from these other two unrelated groups,” said Hugh Beckie, a research scientist with Agriculture Canada.
“That’s something that might be complex to try and understand. We may need to collaborate with other folks to try and find out what’s the underlying biochemical or physiological explanation.”
Other tests with bromoxynil, fluroxypyr and glyphosate found no difference in the performance of resistant and non-resistant plants.
“Based on this greenhouse study, we feel that glyphosate will have no effect either way in terms of control of Group 2-resistant kochia,” said Beckie.
He expects the study will move into field trials next year as researchers look to better understand the magnitude of the response to these chemicals.
“The potential is perhaps reduced herbicide use when they’re applying herbicides from those two groups,” said Beckie.
“But, again, we have to validate these greenhouse findings first before we can make any recommendations.”
